Male external catheters are commonly formed by dipping a mandrel into latex baths and curing the latex between successive dipping operations to build up a catheter wall of desired thickness. Thereafter, the catheter is removed, usually by rolling it off of the mandrel so that it assumes a rolled condition in which it is subsequently marketed.
While the latex-dipping steps are conventional and are similar to those carried out in the manufacture of latex gloves, the further requirement that such a catheter be internally lined with a band of pressure-sensitive adhesive complicates manufacturing operations. Further complications arise from the fact that the provision of such an adhesive coating also requires the outer surface of the catheter to be treated with a suitable release agent so that when the catheter is rolled into its marketed form it may later be unrolled by the user.
The extent of such complexities is illustrated by published International Application WO 86/00816 based on PCT application PCT/DK85/00068. There the steps of applying the inner adhesive layer and the outer release layer are performed only on a pre-formed catheter. In one version an adhesive strip 5 is first wrapped about a mandrel 7 having ducts for the discharge of air under pressure (FIG. 5). A catheter is fitted upon the mandrel while air is simultaneously discharged from the ducts to expand the catheter and prevent its inner surfaces from prematurely contacting the adhesive strip. When the catheter is in place, the flow of air is discontinued and the catheter is allowed to contract into contact with the adhesive. Thereafter, a release layer strip 6 is wrapped about the outer surface of the catheter, and the catheter is finally rolled off of the mandrel. It is believed apparent that such manufacturing operations are labor-intensive and involve complex manipulation that are not easily automated.
U.S. Pat. No. 4,475,910 also discloses a manufacturing method in which an inner adhesive layer and an outer release layer are applied to a pre-formed catheter. In that method, the release layer is first applied to the outer surface of a catheter supported by a mandrel and, after the release layer is cured, an adhesive layer is also applied to the outer side of the catheter over the release layer. The patent does not specify just how the pressure-sensitive adhesive layer is applied but, since no mention is made of drying or curing the adhesive, that layer is presumably transferred to the catheter in its final tacky state from an adhesive-bearing transfer strip or the like. While simpler than the procedure described in the aforementioned British application, the methodology disclosed in this patent nevertheless involves steps that are difficult to automate.
Accordingly, a main aspect of this invention lies in providing a method which may be readily automated and performed on a continuous basis (in contrast to batch basis). In its simplest form, a mandrel is exposed to a series of dipping and drying (or curing) steps for purposes of forming the latex catheter and the adhesive and release layers o its opposite surfaces.
A distinctive feature of the method of this invention lies in applying a layer of adhesive, preferably by means of a dipping operation, directly to the non-stick surface of a mandrel during the first step of the manufacturing procedure. Thereafter, by a series of dipping and curing steps, a latex catheter is formed on the same mandrel over the layer of previously-applied adhesive. Following curing of the latex, the mandrel is again dipped, this time in a bath of release agent, to coat the outer surface of the catheter and prevent the adhesive from adhering to the catheter's outer surface when the finished catheter is rolled off of the mandrel.
Therefore, in brief, the method involves the steps of applying a medical-grade, pressure-sensitive adhesive to the release surface portion of a rigid mandrel to form a weakly-adhering adhesive coating thereon, then dipping the mandrel into a latex bath to form a first latex layer over the mandrel and the adhesive coating and curing the latex layer, repeating the latex dipping and curing steps until a desired wall thickness for the catheter has been formed, then dipping the mandrel in a silicone bath to form a release coating upon the catheter, and finally curing the release coating and rolling the finished catheter off of the mandrel.
Other features advantages, and objects of the invention will become apparent from the specification and drawings.